Paper
Catalysis Science & Technology
In our case, the high activity obtained was proposed to
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Conclusions
In this work, we showed that robust 10% CuZnO catalysts allow
both BHMF or DMF products to be obtained with high yields
from HMF. The selectivity was proposed to depend on the
presence of acid sites at the catalyst surface, which might
probably correspond to ZnOx–CuO and/or Zn–O–Cu interfacial
sites. These sites can be formed during the photoassisted
synthesis of the CuZnO catalyst or can be created in situ in the
highly reductive reaction environment. The catalyst prepared at
room temperature through the photoassisted method
possesses acid sites, which enable direct DMF formation. By
contrast, these acid sites were only generated during the
reaction on the catalyst prepared via the classical wet
impregnation method. What is more, we have concluded that
high HMF conversion is possible when Cun+ and Cu0 sites are
present, as Cun+ allows for HMF adsorption via the CO bond,
while Cu0 allows for H2 dissociation and reduction.
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Palkovits, Chem. Eng. Sci., 2017, 173, 455.
Before subsequent reaction cycles, reoxidation of the
CuZnO catalyst needs to be performed, which can lead to the
redispersion of Cu particles. This oxidative treatment allows
one to obtain active and selective catalysts for several
reaction cycles. By contrast, performing the reduction of the
CuZnO catalyst at a high temperature (300–550 °C) before the
reaction can result in CuZn alloy formation and only
marginal HMF conversion can be obtained.
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Conflicts of interest
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There are no conflicts to declare.
Acknowledgements
The authors gratefully acknowledge that this work was
financially supported by a grant from the National Center of
Science (NCN) in Krakow (Poland) (2016/22/E/ST4/00550). This
research was co-funded by the EU Erasmus+ program. T.
Dintzer and V. Papaefthimiou (ICPEES) are thanked for
performing SEM and XPS analysis, respectively. C. Lefèvre
(IPCMS Strasbourg) and W. Maniukiewicz (LUT) are thanked
for contributing to XRD.
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Catal. Sci. Technol.
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